According to the more detailed data for January 2025, published by the Kraftfahr-Bundesamt:

  Model 3   272
  Model S    13
  Model X    13
  Model Y   979
  ∑        1277

For comparison the data for January 2024:

  Model 3   695
  Model S    31
  Model X    33
  Model Y  2393
  ∑        3152

Model Y in both Januaries is still a multiple of ~ 3.5 of the Model 3.

Your theory, that people were waiting for the MY refresh doesn’t seem likely. According to my experience most people aren’t as much informed of the inside baseball when a new model arrives. Nerd stuff.

Edit, Sources, the F10 Excel spreadsheets here:

2025: https://www.kba.de/DE/Statistik/Fahrzeuge/Neuzulassungen/Mon...

2024: https://www.kba.de/DE/Statistik/Fahrzeuge/Neuzulassungen/Mon...